架构师训练营第五周作业

import java.util.*;
/**
 * 类说明：
 */
public class ConsistentHash {
    private static final int DEFAULT_NOTES = 5;
    private static String[] servers = {"196.168.0.1:111","192.168.0.2.:111","192.168.0.3:111","192.168.0.4:111"};
    private static SortedMap<Integer, String> virtualNodes = new TreeMap<>();
    private static List<String> realNodes = new LinkedList<>();
    static{
        for (int i = 0; i < servers.length; i++) {
            realNodes.add(servers[i]);
        }
        for (String str : realNodes) {
            int realHash = getHash(str);
            int realInterval = Integer.MAX_VALUE / DEFAULT_NOTES;
            for (int i = 0; i < DEFAULT_NOTES; i++) {
                String virtualNodeName = str + "&&VN" + String.valueOf(i);
                int hash = (realHash + realInterval * i) & Integer.MAX_VALUE;
                System.out.println("[" + virtualNodeName + "]加入集合中，其Hash值为：" + hash);
                virtualNodes.put(hash, virtualNodeName);
            }
        }
        System.out.println();
    }
    private static String getServer(String key){
        int hash = getHash(key);
        SortedMap<Integer, String> tailMap = virtualNodes.tailMap(hash);
        if (tailMap.isEmpty()) {
            long serverKey = virtualNodes.firstKey();
            return virtualNodes.get(serverKey);
        } else {
            long serverKey = tailMap.firstKey();
            return virtualNodes.get(serverKey);
        }
    }
    /**
     * 使用FNV1_32_HASH算法计算服务器的Hash值,这里不使用重写hashCode的方法，最终效果没区别
     * 从网上借鉴的
     */
    private static int getHash(String str) {
        final int p = 16777619;
        int hash = (int) 2166136261L;
        for (int i = 0; i < str.length(); i++) {
            hash = (hash ^ str.charAt(i)) * p;
        }
        hash += hash << 13;
        hash ^= hash >> 7;
        hash += hash << 3;
        hash ^= hash >> 17;
        hash += hash << 5;
        // 如果算出来的值为负数则取其绝对值
        if (hash < 0) {
            hash = Math.abs(hash);
        }
        return hash;
    }
}